1. Field of the Invention
The present invention relates to a silver powder for a silver clay having superior sintering characteristics at low temperatures and a silver clay that contains this silver powder.
2. Description of Related Art
Generally, silver ornaments and artworks are manufactured by using casting or forging. However, in recent years, a clay that contains silver powder (Ag powder) has become commercially available, and a method has been proposed wherein the silver ornaments or artworks having a predetermined shape are manufactured by molding this silver clay into a predetermined shape, and sintering it. According to this method, by using the silver clay, it is possible to carry out free molding in a manner identical to that of normal clay craftwork. After the molded article obtained by molding is dried, it is sintered in a sintering furnace, and thereby it is possible to manufacture silver ornaments and artworks extremely easily.
A conventional silver clay is known that consists of a silver powder having a high purity of 99.99 weight % and an average particle diameter of 3 to 20 μm incorporated at 50 to 95 weight %, a cellulose water soluble binder at 0.8 to 8 weight %; an oil at 0.1 to 3 weight %, a surface active agent at 0.03 to 3 weight %; with the remainder being water (refer to Japanese Unexamined Patent Application, First Publication No. Hei 4-26707).
When the conventional silver clay is used, a sintered article that has sufficient strength cannot be obtained unless the temperature is maintained at or above the melting point of silver while being sintered in an electrical furnace after the molded article made of the silver clay has dried. It is possible to obtain a sufficiently strong sintered article if the electrical furnace used to sinter the silver clay has a capacity that can maintain a sufficiently high temperature inside the furnace. However, because individually owned electrical furnaces frequently are small scale and have a low heat capacity, it is not possible to maintain the temperature in the furnace at or above the melting point of silver, and as a result, a sintered article having sufficient density cannot be obtained.
In addition, even if the electrical furnace can maintain a sufficiently high temperature, frequently it is not possible to control the temperature inside the furnace accurately, and as a result, when the temperature in the furnace becomes too high, the shape of the sintered article becomes distorted.